msv_list_servers_demo.c

// ---------- Copyright John Chandara, all rights reserved. ------------- //
//
// Purpose: Demonstrate receiving UDP messages from the HL2 master server.
//
// ---------------------------------------------------------------------- //

#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>



// https://developer.valvesoftware.com/wiki/Master_Server_Query_Protocol#Region_codes
#define REGION_NA_E   0x00 // US East coast
#define REGION_NA_W   0x01 // US West coast
#define REGION_SA     0x02 // South America
#define REGION_EU     0x03 // Europe
#define REGION_AS     0x04 // Asia
#define REGION_AU     0x05 // Australia
#define REGION_ME     0x06 // Middle East
#define REGION_AF     0x07 // Africa
#define REGION_ALL    0xFF // All

// https://developer.valvesoftware.com/wiki/Master_Server_Query_Protocol#IP:Port
#define ID_INITIAL    "0.0.0.0:0"

// https://developer.valvesoftware.com/wiki/Master_Server_Query_Protocol#Filter
#define FILTER_TF2   "\\napp\\440"


#define MAXLEN 1023

int build( char* buf, char region, char *id, char *filters )
{
  return snprintf(buf, MAXLEN, "%c%c%s%s", '1', region, id, filters);
}

void hex_dump ( const char * desc, const void * addr, const int len, int perLine) 
{
  // Silently ignore silly per-line values.

  if (perLine < 4 || perLine > 64) perLine = 16;

  int i;
  unsigned char buff[32];
  const unsigned char * pc = (const unsigned char *)addr;

  // Output description if given.

  if (desc != NULL) printf ("%s:\n", desc);

  // Length checks.

  if (len == 0) {
    printf("  ZERO LENGTH\n");
    return;
  }
  if (len < 0) {
    printf("  NEGATIVE LENGTH: %d\n", len);
    return;
  }

  // Process every byte in the data.

  for (i = 0; i < len; i++) {
    // Multiple of perLine means new or first line (with line offset).

    if ((i % perLine) == 0) {
      // Only print previous-line ASCII buffer for lines beyond first.

      if (i != 0) printf ("  %s\n", buff);

      // Output the offset of current line.

      printf ("  %04x ", i);
    }

    // Now the hex code for the specific character.
    printf (" %02x", pc[i]);

    // And buffer a printable ASCII character for later.
    if ((pc[i] < 0x20) || (pc[i] > 0x7e)) // isprint() may be better.
      buff[i % perLine] = '.';
    else
      buff[i % perLine] = pc[i];
    buff[(i % perLine) + 1] = '\0';
  }

  // Pad out last line if not exactly perLine characters.
  while ((i % perLine) != 0) {
    printf ("   ");
    i++;
  }

  // And print the final ASCII buffer.
  printf ("  %s\n", buff);
}

int fails_challenge_test (const void * addr)
{
  const int challenge[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0x66, 0x0A };
  const int offset = 6;
  const unsigned char * pc = (const unsigned char *)addr;

  // Verify integrity challenge first.
  int i;
  for (i = 0; i < offset - 1; i++) {
    if (pc[i] != challenge[i])
    {
      return 1;

    }
  }

  return 0;

}

void response_dump (const void * addr) 
{
  // Silently ignore silly per-line values.

  const int len = MAXLEN;
  const int perLine = 6;
  const int offset = perLine * 1;

  int i;
  unsigned char buff[perLine+1];
  const unsigned char * pc = (const unsigned char *)addr;

  if (fails_challenge_test(addr)) {
    fprintf(stderr, "E: Response data failed integrity check. Abort processing.");
    return;
  }

  // Process everything after challenge.
  for (i = offset; i < len; i++) {
    // Multiple of perLine means new or first line (with line offset).

    if ((i % perLine) == 0) {
      sprintf(&buff[i % perLine], "%d.%d.%d.%d:%hu", 
          pc[i],
          pc[i + 1],
          pc[i + 2],
          pc[i + 3],
          (pc[i + 4] << 8) + pc[i + 5]
        );

      // Only print previous-line ASCII buffer for lines beyond first.

      if (i != offset) printf ("  %s\n", buff);

      // Output the offset of current line.

      printf ("  %04x ", i);
    }

    // Now the hex code for the specific character.
    printf (" %02x", pc[i]);

    // And buffer a printable ASCII character for later.
    if ((pc[i] < 0x20) || (pc[i] > 0x7e)) // isprint() may be better.
      buff[i % perLine] = '.';
    else
      buff[i % perLine] = pc[i];

    buff[(i % perLine) + 1] = '\0';
  }

  // Pad out last line if not exactly perLine characters.
  while ((i % perLine) != 0) {
    printf ("   ");
    i++;
  }

  // And print the final ASCII buffer.
  printf ("  %s\n", buff);
}


void resolve_hostname (const char *hostname, char *buf)
{
  int socket_fd;
  struct addrinfo hints, *info;

  int result;
  int _test;

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET;
  hints.ai_socktype = SOCK_DGRAM;

  _test = getaddrinfo(hostname, "udp", &hints, &info);
  if (_test)
  {
    fprintf(stderr, "E: %s\n", gai_strerror(_test));
    exit(1);
  }

  struct addrinfo *ptr;
  struct sockaddr_in *addr;
  for (ptr = info; !ptr; ptr->ai_next)
  {
    addr = (struct sockaddr_in *) ptr->ai_addr;
    printf("%s\n", inet_ntoa(addr->sin_addr));
    strncpy(buf, inet_ntoa(addr->sin_addr), 15);
    break;
  }

  freeaddrinfo(info);
}


int main () {
  int socket_fd;
  struct sockaddr_in server_addr, client_addr;
  int _test, _len;

  // 1. Create UDP socket
  printf("Demo: Creating socket... ");
  _test = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (_test < 0)
  {
    fprintf(stderr, "E: Failed to create socket.");
    close(_test);
    return 1;
  } socket_fd = _test;

  // 2. Set port and IP
  // char host[16]; resolve_hostname("hl2master.steampowered.com", host);
  // ;; ANSWER SECTION:
  // hl2master.steampowered.com. 2233 IN	A	208.64.201.194
  // hl2master.steampowered.com. 2233 IN	A	208.64.200.65
  // hl2master.steampowered.com. 2233 IN	A	208.64.201.193
  char host[] = "208.64.201.193";
  server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons(27011);
  server_addr.sin_addr.s_addr = inet_addr(host);

  printf("contacting %s:%d ... \n", host, 27011);

  // 3. Send query to server
  socklen_t addr_len = (socklen_t) sizeof(struct sockaddr_in);
  char cl_buffer[MAXLEN]; memset(cl_buffer, '\0', MAXLEN);
  char sv_buffer[MAXLEN]; memset(sv_buffer, '\0', MAXLEN);

  _len = build(cl_buffer, REGION_NA_E, ID_INITIAL, FILTER_TF2);
  _test = sendto(socket_fd, cl_buffer, _len + 1, 0,
      (struct sockaddr*) &server_addr, addr_len);
  if (_test < 0)
  {
    fprintf(stderr, "E: Failed to send query to master server.\n");
    close(socket_fd);
    return _test;
  }

  printf("Demo: Sent search query!\n");

  // 4. Receive client messages
  _test = recvfrom(socket_fd, sv_buffer, MAXLEN, 0,
      (struct sockaddr*) &server_addr, &addr_len);
  if (_test < 0)
  {
    perror("E: ");
    close(socket_fd);
    return 1;
  }

  printf("Demo: Response.\n");

  response_dump(sv_buffer);

  printf("\nDemo: Successfully queried master server.\n");

  // 5. Close socket
  close(socket_fd);

  return 0;
}